Buildless single-page browser simulation. Open `index.html`; no package manager, transpiler, server API, or module loader is required. Runtime order is explicit `<script defer>` order generated from `app_manifest.json`. Current inspected version: `15.20.16`.
- Startup uses a loading overlay that eagerly preloads a small sprite set, initializes UI/world state, then defers remaining image work.
- Field choices are cage, garden, and park. `FIELD_TYPES` controls world scale, starting population, initial grass count, and responsive field height.
- The default field is garden. Reset opens the field dialog; cancel keeps the current field.
- Tools are grouped in collapsible categories: operation/observation, food/water/grass, medicine/effects, habitat/living things, hazards/obstacles.
- The top bar owns pause, speed, ecology, sound, credits, and reset controls. Event push toasts live inside the Event card, while sound category toggles live only in the sound menu.
- The colony panel charts population, mental state, environment, and object counts. The family tree is a separate main section with manual/auto refresh and reset controls.
- Mobile operation modes are available only on compact touch-first phone viewports: auto, camera, tool, family.
- Weather rain overlay is diagonal line streaks. Fallen water items, zunda juice, and mercury share the same horizontal oval item-droplet silhouette; recolor only.
- Tool UI icons must be generated previews of `js/items.js` drawing helpers, never separate designs.